Isolation bearings are generally used to protect, for example, bridges, buildings, computers, machines, delicate and/or dangerous equipment, and the like from damage due to seismic vibrations. The isolation bearings (and platforms and floors containing such isolation bearings) are typically configured to support a specific load, i.e., the mass and load distribution of the payload being supported.
As one example, given a support surface (such as a floor or platform) having upright support pedestals positioned at the corners of a 600 mm by 600 mm grid, a payload having a specified large mass distributed over a single 600 mm×600 mm (0.36 m2) grid unit is supported by 4 such supports. The same load distributed over a larger surface area (1200 mm×1200 mm, or 4 such grid units) is supported by 9 upright supports; thus, the mass required to be supported by each support in the smaller grid is more than twice (2.25 times in the example above) the mass required to be supported by an individual support in the original surface area.
For this reason, raised flooring systems that are sufficiently strong and robust for early computer rooms and data centers, (in which hot and cold aisles were not designed and almost all the floor space could be used for IT, mainframe, batteries and other computer-related equipment) are often not strong and robust enough for the highly load-concentrated, often multi-tiered rack-mounted payloads in present-day data centers employing hot and/or cold aisle cooling systems. Furthermore, raised flooring systems are typically used to provide ventilation and under-floor space for the provision of services to the supported payload. Such services include, without limitation, conduit or cable for electrical power, data transfer, fluid (such as cooling and fire suppression fluids) and lighting) to the payload.
A typical computer stand or platform is manufactured by California Dynamics Corp. (CalDyne) and marketed as the Type LW Floor Stand: (www.caldyn.com/content/products/computer_room/floor_stands/lw/lw.pdf). This floor stand is a relatively lightly constructed rectangular box, having L-shaped corner supports that appear to be made from a bent steel plate, and a pair of intermediate supports made from steel plate. The top and bottom perimetric frames, and the framework components providing internal support, are made of thinner steel framing material. The corner supports and intermediate supports are fastened to this framing material and to the floor via elastomer-padded foot plates. The foot plates are, in turn anchored into the floor using anchor bolts; in some examples, a spring or elastomeric material may provide dampening against payload damage due to seismic vibrations. The feet can be leveled, i.e. during or after installation, using threaded leveling screws or bolts.
Two approaches have been traditionally utilized to prevent or limit damage or injury to objects or payloads due to seismic events. In the first approach, used particularly with structures themselves, the objects or payload articles are made strong enough to withstand the largest anticipated earthquake. This is the basic approach of the CalDyne Floor Stand and similar raised platforms or flooring systems. However, in addition to the relative inability to predict the extent of damage caused by tremors of high magnitude and long duration and of the directionality of shaking, use of this method alone can be quite expensive and is not necessarily suitable for payloads which are to be housed within a structure. Particularly for delicate, sensitive or easily damaged payload, this approach alone is not especially useful.
In the second approach, the objects are isolated from the vibration such that the objects fail to experience the full force and acceleration of the seismic shock waves. Various methods have been proposed for accomplishing isolation or energy dissipation of a structure or object from seismic tremors, and these methods may depend in some measure on the nature of the object to be isolated.
Thus, particularly for very massive payloads, such as buildings, bridges, and other structures, payloads may be isolated using, for example, passive systems, active systems, or hybrid systems. Such systems may include the use of one or more of a torsional beam device, a lead extrusion device, a flexural beam device, a flexural plate device, and a lead-rubber device; these generally involves the use of specialized connectors that deform and yield during an earthquake. The deformation is focused in specialized devices and damage to other parts of the structure are minimized; however the deformed devices often must be repaired or replaced after the seismic event, and are therefore largely suitable for only one use.
Active control systems require an energy source and computerized control actuators to operate braces or dampers located throughout the structure to be protected. Such active systems are complex, and require service or routine maintenance.
For objects other than such massive payloads, isolation platforms or flooring systems may be preferable to such active or deformable devices. Thus, for protection of delicate or sensitive payloads such as manufacturing or processing equipment, laboratory equipment, battery power plants, computer servers and other hardware, optical equipment and the like an isolation system may provide a simpler, effective, and less maintenance-intensive alternative. Isolation systems are designed to decouple payloads from damage due to the seismic ground motion.
Seismic isolators have a variety of designs. Thus, such systems have generally comprised a combination of some or all of the following features: a sliding plate, a support frame slidably mounted on the plate with low friction elements interposed therebetween, a plurality of springs and/or axial guides disposed horizontally between the support frame and the plate, a floor mounted on the support frame through vertically disposed springs, a number of dampers disposed vertically between the support frame and the floor, and/or a latch means to secure the vertical springs during normal use.
Certain disadvantages to such pre-existing systems include the fact that it is difficult to establish the minimum acceleration at which the latch means is released; it is difficult to reset the latch means after the floor has been released; it may be difficult to restore the floor to its original position after it has moved in the horizontal direction; the dissipative or damping force must be recalibrated to each load; there is a danger of the stand or floor rocking on the vertical springs; and since the transverse rigidity of the vertical springs cannot be ignored with regard to the horizontal springs, the establishment of the horizontal springs and an estimate of their effectiveness, are made difficult.
Ishida et al., U.S. Pat. No. 4,371,143 have proposed a sliding-type isolation floor that comprises length adjustment means for presetting the minimum acceleration required to initiate the isolation effects of the flooring in part by adjusting the length of the springs.
Yamada et al., U.S. Pat. No. 4,917,211 discloses a sliding type seismic isolator comprising a friction device having an upper friction plate and a lower friction plate, the friction plates having a characteristic of Coulomb friction, and horizontally placed springs which reduce a relative displacement and a residual displacement to under a desired value. The upper friction plate comprises a material impregnated with oil, while a lower friction plate comprises a hard chromium or nickel plate.
Stahl (U.S. Pat. No. 4,801,122) discloses a seismic isolator for protecting e.g., art objects, instruments, cases or projecting housing comprising a base plate connected to a floor and a frame. A moving pivoted lever is connected to a spring in the frame and to the base plate. The object is placed on top of the frame. Movement of the foundation and base plate relative to the frame and object causes compression of the lever and extension of the spring, which then exerts a restoring force through a cable anchored to the base plate; initial resistance to inertia is caused due to friction between the base plate and the frame.
Kondo et al., U.S. Pat. No. 4,662,133 describes a floor system for seismic isolation of objects placed thereupon comprising a floor disposed above a foundation, a plurality of support members for supporting the floor in a manner that permits the movement of the floor relative to the foundation in a horizontal direction, and a number of restoring devices comprising springs disposed between the foundation and the floor member. The restoring members comprise two pair of slidable members, each pair of slidable members being movable towards and away from each other wherein each pair of slidable members is disposed at right angles from each other in the horizontal plane.
Stiles et al., U.S. Pat. No. 6,324,795 disclose a seismic isolation system between a floor and a foundation comprising a plurality of ball and socket joints disposed between a floor and a plurality of foundation pads or piers. In this isolation device, the bearing comprises a movable joint attached to a hardened elastomeric material (or a spring); the elastic material is attached on an upper surface of the ball and socket joint and thus sandwiched between the floor and the ball and socket joint; the bearing thus tilts in relation to the floor in response to vertical movement. The floor is therefore able to adjust to buckling pressure due to distortion of the ground beneath the foundation piers. However, the device disclosed is not designed to move horizontally in an acceleration-resisting manner.
Fujimoto, U.S. Pat. No. 5,816,559 discloses a seismic isolation device quite similar to that of Kondo, as well as various other devices including one in which a rolling ball is disposed within the tip of a strut projecting downward from the floor in a manner similar to that of a ball point pen.
Bakker, U.S. Pat. No. 2,014,643, is drawn to a balance block for buildings comprising opposed inner concave surfaces with a bearing ball positioned between the surfaces to support the weight of a building superstructure.
Kemeny, U.S. Pat. No. 5,599,106 discloses ball-in-cone bearings.
Kemeny, U.S. Pat. Nos. 7,784,225 and 8,104,236 discloses seismic isolation platforms containing rolling ball isolation bearings.
Hubbard and Moreno, U.S. Pat. Nos. 8,156,696 and 8,511,004 discloses apparatus and methods involving raised access flooring structure for isolation of a payload placed thereupon.
Moreno and Hubbard, U.S. Pat. No. 8,342,752 disclose isolation bearing restraint devices.
Isolation bearings are disclosed in Hubbard and Moreno, U.S. Patent Publication US 2013/0119224 filed on Sep. 25, 2012.
Moreno and Hubbard, U.S. Patent Publication No. U.S. 2011/0222800 discloses methods and compositions for isolating a payload from vibration.
Moreno and Hubbard, U.S. Pat. No. 9,109,357 B2 discloses modular isolation systems and preferred seismic isolation systems not having a raised floor structure, but rather having a low profile permitting the resulting seismic isolators to be substantially level with, or slightly above, the existing flooring surrounding structure.
Moreno and Hubbard U.S. Patent Publication No. US 2015/0128510 A1 describes polygonal seismic isolation bearings.
Hubbard and Moreno, U.S. Provisional Patent Application Nos. 62/079,475, 62/262,816 and 62/335,203 describe seismic isolation of container transport and storage systems.
Moreno and Hubbard, U.S. Provisional Patent Application Ser. No. 62/346,182, filed Jun. 6, 2016 and entitled “Seismic Isolation Systems Comprising A Load-Bearing Surface Having A Polymeric Material” describes isolators having a polymeric coating.
Chen, U.S. Pat. No. 5,791,096 discloses a raised floor system.
Denton, U.S. Pat. No. 3,606,704 discloses an elevated floor structure suitable for missile launching installations with vertically compressible spring units to accommodate vertical displacements of the subfloor.
Naka, U.S. Pat. No. 4,922,670 is drawn to a raised double flooring structure which is resistant to deformation under load. The floor employs columnar leg members that contain a pivot mounting near the floor surface, which permits to floor to disperse a load in response to a side load.
All patents, patent applications and other publications cited in this patent application are hereby individually incorporated by reference in their entirety as part of this disclosure, regardless whether any specific citation is expressly indicated as incorporated by reference or not.
The conservative character of a seismic isolation bearing may be described in terms of the bearing's ability to absorb displacement energy against the gravitational force caused by seismic activity or other external applied forces, and thus to cushion the structure being supported from such displacement. In this regard, features such as a rubber bearing body, leaf spring, coil spring, or the like may be employed to urge the bearing back to its original, nominal position following a lateral displacement caused by an externally applied force such as a seismic tremor. In this context, the bearing “conserves” lateral displacement energy by storing a substantial portion of the applied energy, and releases this stored energy upon cessation of the externally applied force to pull or otherwise urge the bearing back to its nominal original position.
Certain isolation bearings may have a laminated rubber bearing body, reinforced with steel plates. More particularly, thin steel plates may be interposed between relatively thick rubber plates, to produce an alternating steel/rubber laminated bearing body. The use of a thin steel plate between each rubber plate in the stack helps prevent the rubber from bulging outwardly at its perimeter in response to applied vertical bearing stresses. This arrangement permits the bearing body to support vertical forces much greater than would otherwise be supportable by an equal volume of rubber without the use of steel plates.
Other isolation bearings may comprise steel coil springs combined with snubbers (i.e., shock absorbers). These bearings are often used to vertically support the weight of the payload. Coil springs, described in International Patent Publication WO 2004/007871, are generally preferable to steel/rubber laminates in applications where the structure to be supported may undergo an upward vertical force, which might otherwise tend to separate the steel/rubber laminate. Rubber bearings are typically constructed of high damping rubber, or are otherwise supplemented with lead or steel yielders useful in dissipating applied energy.
Metallic yielders, however, are disadvantageous in that they inhibit or even prevent effective vertical isolation, particularly in assemblies wherein the metallic yielder is connected to both an upper bearing plate and an oppositely disposed lower bearing plate within which the rubber bearing body is sandwiched.
Steel spring mounts of the type typically used in conjunction with the isolation of payloads comprising apparatus and/or machines are generally unable to provide adequate energy dissipation, with the effect that such steel spring mounts generally result in wide bearing movements or oscillations. Such wide bearing movements may be compensated for through the use of snubbers or shock absorbers to aid in absorbing the energy of the lateral displacement. However, in use, the snubber may impart to the bearing an acceleration on the order of, or even greater than, the acceleration applied to the machine due to seismic activity alone.
In another example, an isolation bearing may comprise a lower plate having a concave (having an arc-shaped cross sectional portion) shaped cavity and an upper plate having a substantially identical cavity with a rigid ball placed therebetween.
In yet another example, such a seismic isolation device includes a bearing comprising a lower plate having a parabolic shaped cavity and an upper plate having a substantially identical cavity with a rigid ball placed therebetween.
Isolation platforms having seismic bearings containing a variety of differently shaped load bearing surfaces are disclosed in e.g., International Patent Publication No. WO/2004/007871 and US 2006/0054767; Isolation platforms comprising floors are disclosed in e.g., U.S. Pat. No. 7,290,375. Each of these publications and patents, and every other patent, patent application, and publication cited in this patent application, is expressly and individually incorporated by reference herein in its entirety as part of this specification.
Isolation bearings of the “rolling ball” type may in general include a lower plate having, without limitation, a conical, concave or parabolic shaped cavity, or a combination of linear and curved shapes in cross-section; a cavity having a region of constant or variable slope and an upper plate which may be different from, or preferably identical to, the lower plate, with a rigid ball or other rolling member (such as one or more cylindrical rod, placed therebetween. The lower plate rests or is fixed or placed on the ground, foundation, platform, support, floor or base surface, while the payload to be supported rests directly or indirectly on the top surface of the upper plate, or the platform or surface which is supported by the isolation bearing or bearings. In this way, when external vibrations such as seismic movements occur the lower plate moves relative to the upper plate via the rolling of the spherical ball between the upper and lower plates.
There is therefore a continuing need for isolation systems, including isolation platforms and isolation floors, that are strong, robust, and stable (i.e., have a reduced tendency to collapse or come apart in use), and which can withstand high weight concentrations of payloads such as, without limitation, information technology (IT) equipment, data center computer equipment, racks containing such equipment, which may include servers, hard disk drives (HDD), batteries for backup power, and the like, and absorb both large seismic shocks and smaller amplitude vibrations. Preferably the isolation systems are also quickly easily integrated into the locations in which they are desired to be installed.
There is also a need for isolation platforms and flooring systems which are both modular and standardized, and yet able to be quickly assembled and flexible enough to be partly or completely reconfigured to meet changing layout requirements. For example, U.S. Patent Publication No. US 2015/0128510 A1 and U.S. Provisional Patent Application Ser. No. 62/346,182, filed Jun. 6, 2016 describe seismic isolation bearings having, in a top view a non-rectangular polygonal frame or border containing fastener fittings (such as, without limitation, pins and/or bolt holes), which easily permits the quick, firm attachment of framing elements to the isolation bearings at a variety of angles. This allows the customizable assembly of isolation racks, supports and flooring to suit a large variety of floor plans, including “curved” and other non-standard floor plans. Additionally, the use of polygonal fittings isolation bearings permits the easy design of a floorplan that accommodates vertically extending features such as building columns pipes, conduit, and the like.